I'm afraid we can't offer support for using Viscosity on beta versions of macOS. That said, we've tested Viscosity on macOS 10.13.4 beta 5 and didn't find any connection issues, so it's likely unrelated. I recommend you check any firewall etc. software and also check the items listed in the following article:https://www.sparklabs.com/support/kb/ar ... 0-seconds/